With the wide use of electronic equipment, the use of power banks becomes more and more popular. The charging power of an existing power bank is determined by a charger. If the charger used is not the originally packaged charger, the related parameters of the provided charging current will be changed, or the external power supply itself will fluctuate, and the variation of the charger may cause the charging power to be higher than the power of the power bank, so that the power bank may be damaged during charging; and furthermore the fluctuation of the external power supply itself may also influence the service life of the power bank.